The present invention relates to a push button, of the type pressed in by a user in order to actuate a commutator, in particular integrated in a motor vehicle key module, comprising a communication member for opening and closing the doors of the vehicle remotely.
Those push buttons are based on the pressing-in of a movable portion which is caused to move by a pressing effort by a user and is pressed in with respect to a fixed portion, generally the member which carries the button.
The buttons, in particular push buttons, have a line of the effort applied in accordance with the generally increasing pressing-in action, up to a threshold value, at which the effort applied abruptly decreases. That decrease in the effort is felt by the user and this is what is perceived as a “click”, even if the mechanism does not produce any noise, which provides a haptic return reassuring the user that his instruction has been taken into consideration.
The decrease in the effort felt is referred to as the snap effect of the button, which is measured as being the relationship ΔF/F between the decrease in the effort and the absolute value of the maximum effort applied just before the decrease, which is therefore non-dimensionalized.
That snap effect results from the mechanism of the commutators used which have a plurality of states of minimum energy, corresponding to different commutating states which are separated two by two by a potential energy barrier which is overcome by the actuation action. From an initial state, the potential energy maximum is reached at the so-called tipping point, beyond which the mechanism pivots into the final state of its own accord.
It is known to use flexible diaphragms as the resilient element which ensures the return of the movable portion of the push button. Those diaphragms perform a double function in that they allow the return to a rest position of the movable portion, and in that they isolate the electronic commutator from the external environment.
For better actuation of the commutator, the portion of the diaphragm often has an excessive thickness at the surface facing the commutator, acting as a finger pressing in the commutator.
Those structures produce a snap effect in the order of from 15 to 20%.
That perception of the haptic return may be considered to be insufficient in that, generally, a clearly defined snap effect is felt as a sign of quality by a user.